Thin film transistor liquid crystal display (TFT-LCD), due to its advantages of high quality, excellent space utilization, low power consumption, no radiation, small volume and the like, has been widely used.
In image-displaying of TFT-LCD, a nonlinear relationship is presented between grayscale and luminance of a pixel, and a curve reflecting the nonlinear relationship is called Gamma curve, which is a power-law curve with a power-law index called Gamma value. In image-displaying of TFT-LCD, a Gamma voltage generating circuit of the TFT-LCD generates multiple Gamma voltages which are then converted to grayscale voltages which are used for displaying and correspond to respective grayscales. Since backlight luminance, panel materials and the like of different models of TFT-LCDs are not exactly the same, pixels with the same grayscale may present different luminance when the same Gamma voltage is applied, which results in differences between Gamma values of actual Gamma curves of some TFT-LCDs and a target Gamma value (generally is 2.2, and the corresponding curve thereof is referred to as 2.2 curve). The differences determine final displaying effects of the TFT-LCDs (i.e. the smaller the difference is, the better the displaying effect will be).
Therefore, it is necessary to adjust Gamma voltages of a TFT-LCD before the TFT-LCD leaves the factory, so that a Gamma curve whose Gamma value becomes as close to a target Gamma value (generally is 2.2) as possible is obtained and the obtained Gamma curve serves as a preset Gamma curve. As described above, Gamma voltages are generated by a Gamma voltage generating circuit comprising a timing controller, a Gamma IC and other components.
In adjusting Gamma voltages, the Gamma IC is controlled by a personal computer (PC) which is used for changing a Gamma voltage output by the Gamma IC. As for a certain grayscale, the Gamma IC outputs an initial Gamma voltage corresponding to the grayscale, detects pixel luminance under the condition of the initial Gamma voltage, and judges whether a relationship between the grayscale and the detected pixel luminance satisfies a power-law relationship with a power-law index of 2.2. If the power-law relationship is not satisfied, the Gamma IC adjusts the Gamma voltage, detects pixel luminance under the condition of the adjusted Gamma voltage and then judges whether a relationship between the grayscale and the detected pixel luminance satisfies the power-law relationship with the power-law index of 2.2. The above processes are repeated until a final Gamma voltage corresponding to the grayscale is found. Also, Gamma voltages corresponding to other grayscales are sequentially obtained in the same manner as above, thereby finishing adjusting Gamma voltages.
With the development of large-size display panel technology, two or more Gamma ICs are used in an increasing number of large-size display panels, that is, multiple Gamma ICs perform joint control to lighten all pixels.
Inventors found that at least the following problems exist in the prior art: for a display panel in which two or more Gamma ICs are used, when a process of adjusting Gamma voltage is performed thereon, in one aspect, multiple PCs may be used to control Gamma ICs, respectively, but in this case, the adjusting process becomes complicated and time-consuming; in another aspect, the Gamma ICs may be adjusted sequentially, but in this case the process of adjusting Gamma voltage cannot be performed on the entire display panel at the same time and thus an accurate Gamma curve of the entire display panel cannot be obtained through adjustment.